Numerous developments have been made for applications in respiratory therapy. These are generally referred to as "rebreather" devices because a user's exhaled breath directed into some form of chamber is then reinhaled at least in part by the user. One such device is the Adler rebreather as manufactured by the Gaymar Industries, Inc., Buffalo, N.Y. This device is described, for example, in a publication entitled "Diseases of the Chest", Volume 2, Number 5, November, 1967. This device is generally cylindrical, is formed of a rigid plastic, and contains various internal baffles dividing the device into several chambers. The long air passages created by these baffles causes an accumulation of a portion of the carbon dioxide exhaled by a user. As this air is again reused within the body, the elevated level of carbon dioxide causes a stimulation whereby the breathing rate is reduced which, among other results, produces a desirable breathing exercise which assists in post-operative recovery of the user.
Other devices within the class of rebreathers utilize an enclosure in which various medications are mixed with a user's exhaled air and upon further inhaling, the medication is taken into the respiratory system. Typical of these devices are those shown in U.S. Pat. No. 1,044,367 issued Nov. 12, 1912, to G. A. Evans; U.S. Pat. No. 2,321,256 issued to F. L. Shelton on June 8, 1944; and U.S. Pat. No. 2,304,033 also issued to F. L. Shelton on Dec. 1, 1942. These devices, as well as the Adler rebreather, are intended for use with persons while they are substantially immobile, i.e. confined to a chair or a bed.
Recently it has been determined that a slight elevation in the carbon dioxide content of air inhaled by a person reverses temporary hearing threshold shifts due to noise exposure. As used herein, the term "temporary threshold shift" is defined as a reversable loss of hearing sensitivity. Furthermore, subjecting a person to this elevated carbon dioxide air often prevents or minimizes any temporary hearing threshold shifts due to the noise. If the temporary shift is not negated or prevented, permanent hearing damage can occur.
Accordingly, it is an object of the present invention to provide a device which may be used to increase the carbon dioxide content of air breathed by a user to overcome temporary hearing threshold shifts.
It is another object to provide a device which will permit an increase in the carbon dioxide level of the blood whereby a temporary hearing threshold shift due to noise exposure is prevented or reduced.
It is also an object of the present invention to provide a device for preventing or at least reducing temporary hearing threshold shifts due to noise, which device can be carried by a worker who anticipates or is subjected to noise exposure which otherwise may cause a temporary hearing threshold shift.
It is an additional object of the invention to provide a device for use in the prevention and/or stablization of physiological conditions sensitive to increased carbon dioxide concentration in inhaled air, such as pre- and post-operative hypoexpansion of the lungs, etc.
Yet another object of the present invention is to provide a rebreather apparatus which reduces the rate of respiration of a user so as to be an effective treatment for hyperventilation.
It is a further object of the present invention to provide a rebreather apparatus of sufficient rigid construction and yet portable and disposable for use by industrial workers where undue noise may be present.
Other objects and advantages of the invention will become apparent upon a consideration of the detailed description and reference to the drawings.